What else has private equity been buying up, after businesses in prison systems, health care clinics and public water systems? Lately, one answer has been legal directories and rankings publications, which highlight particular law firms or attorneys by practice area.

In the last year, some of the largest legal ranking and search companies have been acquired by private equity firms, including Chambers and Partners and Best Lawyers.

The new ownership has led to concerns among some Am Law 200 chief marketing officers, who wonder whether the companies will be more aggressive in pricing and products, and whether the confidential information that law firms submit to them will be used for new purposes. The executives of two companies with new ownership, however, insist the law firms' data will continue to be treated confidentially, and that they aren't under new orders to pursue high price models.